1. Field of the Invention
The present invention relates to a position detecting apparatus, a position detecting method, an exposure apparatus, and a method for producing a device. In particular, the present invention relates to the position detection for a mask or a photosensitive substrate in an exposure apparatus which is usable in the lithography step of producing an electronic device including semiconductor elements, image pickup elements, liquid crystal display elements, thin film magnetic heads, etc.
2. Description of the Related Art
When a device such as a semiconductor element or the like is produced, a plurality of layers of circuit patterns are formed in an overlapped or overlaid manner on a photosensitive substrate (substrate such as a wafer, a glass plate or the like coated with a photosensitive material). Therefore, in order to perform the relative positional adjustment (alignment) for a pattern of a mask and each of exposure areas of the photosensitive substrate having been already formed with a circuit pattern or patterns in an exposure apparatus for exposing the photosensitive substrate with the circuit patterns, it is necessary to detect the two-dimensional position information taken along a pattern surface of the mask and the two-dimensional position information taken along an exposure surface of the photosensitive substrate. For example, a position detecting apparatus based on the image pickup system has been hitherto suggested in order to detect the two-dimensional position information about the pattern surface of the mask or the exposure surface of the photosensitive substrate. In U.S. Pat. No. 5,783,833,for example, an image pickup element, which is constructed of a CCD camera, is used as an alignment sensor of the off-axis system in order to positionally adjust (align) the mask pattern and the photosensitive substrate. A part of the imaging light flux is received by the image pickup element via a light flux semi-shielding plate.
On the other hand, in order to form a good image (fair image) of a fine pattern of a mask on a photosensitive substrate via a projection optical system, it is necessary for the exposure apparatus to detect the focus position information of the pattern surface of the mask and the focus position information of the exposure surface of the photosensitive substrate taken in the optical axis direction of the projection optical system. In order to detect the focus position information of the pattern surface of the mask or the exposure surface of the photosensitive substrate, for example, a position detecting apparatus of the photoelectric microscope system has been hitherto suggested.